Hubble founds a large galaxy cluster

The Hubble Space Telescope has been in operation since 1990. A team of astronomers used the Hubble to discover a collection of over 250 dwarf galaxies.

Researchers said the galaxies are estimated "only 600-900 million years after the big bang." It may seem a long time already but it's just a pittance on the scale of the universe's life span. NASA notes that it took over 12 billion years for the light from the galaxies to reach the Hubble.

"The faintest galaxies detected in these Hubble observations are fainter than any other yet uncovered in the deepest Hubble observations," says Johan Richard, an astronomer who worked on the project.

Before, the universe was full of thick hydrogen gas. All the gas that once blocked the travel of ultraviolet light in the universe began to clear, creating what scientists call the epoch of reionization. When it cleared, ultraviolet light was able to cover great distances. NASA refers to this as the universe becoming "transparent to ultraviolet light." The small galaxies found are said to be involved in this process.

NASA notes that the galaxies are major actors in keeping the universe transparent. This discovery helped scientists determine that the epoch of reionization came to a close about 700 million years after the big bang.

A joint project between NASA and the European Space Agency, the Hubble has been in operation for over 25 years with no signs of slowing down. It generates a constant stream of fascinating discoveries and beautiful space images.

This year, Hubble delivered some outstanding visuals with fresh looks at the artfully cloudy Lagoon Nebula, the butterfly-like Twin Jet Nebula and a lonely dwarf spiral galaxy.

NASA shared the research on the 250 dwarf galaxies on October 22, 2015. A study on the findings will be published soon in the Astrophysical Journal.